232 E. A. BAUMGARTNER 



In a 9 mm. embryo, Rathke's pouch is widened transversely, 

 but is constricted at its base. The lateral lobes extend dorso- 

 laterally from just below the constricted portion (fig. 64). Their 

 bases are slightly anterior to that of Rathke's pouch. The 

 thickened anterior arm of epithelium has formed a medial out- 

 pouching, anterior to Rathke's pouch (fig. 15). A reconstruction 

 of this region shows, from the oral surface, a cup-like depression 

 and a wide medial opening of Rathke's pouch. On either side, 

 just anterior to this, are the two openings of the lateral lobes. 

 Seessel's pouch is inconspicuous. 



Both laterally and ventrally the carotids come into contact 

 with the lateral lobes. The vein described in the 5 mm. embryo 

 retains the same relations in this embryo, but the anastomosing 

 branch, caudal to Rathke's pouch fuses to form a large venous 

 channel (fig. 15). 



Marked changes have taken place in an 11.6 mm. embryo, 

 where the anterior bud is constricted from the oral roof and the 

 four-lobed hypophysis is attached to the mouth by means of a 

 narrow stalk. Projecting caudo-dorsally to this stalk is an epi- 

 thelial cord which possibly represents Seessel's pouch. The short, 

 hypophyseal stalk extends dorso-cranially and is attached to the 

 ventro-anterior wall of the anterior bud. The caudal lobe, or 

 Rathke's pouch, is closely applied to the small infundibular 

 outgrowth and has a flattened tip. Rathke's pouch is markedly 

 constricted where it joins the large anterior bud (fig. 16). The 

 latter is closely applied to the floor of the brain. On either side, 

 between these two parts, lie the short, finger-like lateral lobes 

 extending upward, but not in contact with the floor of the brain. 

 Below they open into the cavity of the anterior lobe, which 

 widens to receive them. Caudal to the constricted portion of 

 Rathke's pouch is an oval-shaped mass of cartilage which con- 

 tains the tip of the notochord. Lateral cartilaginous masses 

 extending anteriorly are continuous with that mentioned above. 

 Dorsal to the anterior end of the lateral masses and cranial to 

 the anterior lobe, is a condensed connective tissue or precarti- 

 laginous mass. It projects upward to the brain floor and for- 

 ward to the optic chiasma. A fibrous band of connective tissue 



